Air-flow generating device for a sheet delivery of a sheet-fed printing machine

ABSTRACT

Sheet delivery for a sheet-processing machine having a sheet-conveying device for successively conveying sheets to a device for receiving a sheet pile thereon, includes a device disposed above the sheet-pile receiving device for generating an air flow to facilitate with air a depositing of the sheets upon the pile-receiving device, the air-flow generating device having an air-supplied air-volume chamber having a basal surface and formed with outlet openings distributed over the basal surface thereof, the basal surface having an area corresponding approximately to a maximum sheet format.

The invention relates to a sheet delivery for a sheet-processingmachine, more particularly, a sheet-fed printing machine having asheet-conveying device for conveying sheets successively to a device forreceiving a pile of the sheets, an air-flow generating device beingdisposed above the sheet pile-receiving device for facilitating with airsheet-deposition onto the pile.

Sheet deliveries of conventional sheet-fed printing machines,respectively, have a delivery gripper system guiding the printed sheetsto a sheet pile (delivery pile). In order to achieve the formation of aprecise pile, it has become known heretofore to use an air-generatingdevice which is disposed above a device for receiving the sheet pile (adelivery table, paper stops, and so forth), by which the sheets,released by the grippers of the delivery gripper system and delayed bymeans of a sheet braking device, are subjected to air for the purpose ofincreasing the velocity of the descent of the sheets which are beingdeposited.

Such an air-flow generating device is disclosed in German PublishedNon-Prosecuted Patent Application (DE-OS) 34 13 179 as having severalblowers which are distributed over a maximally possible sheet formatarea and which are activated in accordance with the demand. The rotaryspeeds of the individual blowers or fans may be adjusted in accordancewith the intensity of the respective desired air flow. Moreover, it ishas become known heretofore from the aforementioned German patentapplication to provide, in addition to the blowers, air blast orblowing-air pipes or tubes which, in combination, form air blast orblowing-air rakes having, over the lengths thereof, small bores formedtherein through which, respectively, a targeted air flow escapes.

The air-flow generating device heretofore known from the German patentapplication fails to meet adequately the different requirementsdependent upon paper thickness, ink application, subject or motifformation, printing format, and so forth; in particular, at highprinting speeds, the limits of such systems are readily revealed.

It is accordingly an object of the invention to provide a sheet deliveryof the aforementioned general type with an air-flow generating devicewhich ensures an optimum and very rapid sheet delivery under alloperating conditions. More-over, a particularly simple construction forthe device is sought after.

With the foregoing and other objects in view, there is provided inaccordance with the invention, a sheet delivery for a sheet-processingmachine having a sheet-conveying device for successively conveyingsheets to a device for receiving a sheet pile thereon, comprising adevice disposed above the sheet-pile receiving device for generating anair flow to facilitate with air a depositing of the sheets upon thepile-receiving device, the air-flow generating device having anair-supplied air-volume chamber having a basal surface and formed withoutlet openings distributed over the basal surface thereof, the basalsurface having an area corresponding approximately to a maximum sheetformat.

In contrast with the state of the art, no individual blowers andadditional blowing-air rakes are provided in the sheet deliveryaccording to the invention; but rather, the maximum sheet-format range,which depends, in each case, upon the type of sheet-fed printingmachine, is covered by the basal surface of the air-volume chamber, withoutlet openings distributed over the basal surface ensuring that therespective sheet is subjected to a selective air flow. The plurality ofpartial air flows which escape through the individual outlet openingsand act upon a respective sheet ensure that the sheet descends or islowered at high depositing speed and that the position at which it isdeposited or delivered is precise and reproducible. This results inprecise pile formation, even at very high printing speeds.

The inventive air-volume chamber represents a material constructionsimplification in comparison with the conventional complexstate-of-the-art arrangement of blowers, with air-blast or blowing-airpipes disposed between the blowers. The air-volume chamber may besupplied with air by the air-pressure device which is always availablein sheet-fed printing machines, or by a separate central compressor orblower unit. Because the basal surface of the air-volume chambercorresponds approximately to the maximally possible sheet format of therespective sheet-fed printing machine, it is possible always to depositor deliver sheets of any sheet format, even maximum sheet sizes, exactlyand rapidly.

In accordance with another feature of the invention, covering means areincluded for sealing at least some of the outlet openings so as toadjust air-flow intensity and/or air diffusion of air escaping from theair-volume chamber. The covering means permits the respective sheet tobe concretely blown-on independently of the sheet format and/or themotif or subject thereof, and so forth. Wavy regions of the sinking ordescending sheets, for example, are able to be blown-on by partial airflows escaping through respective outlet openings, so that a sheetdeposit or delivery in a stable position, for example, in a V position,is possible. Due to the covering means, it is possible, among otherthings, to adapt the air-escape range to the individual sheet sizes,which ensures a more accurate control and, moreover, lowers airconsumption and the energy cost thereof. Adjusting to the respectiveprint-job sheets takes only very little time and is not complicated,because only those outlet openings which are not needed to generate theair flow for sheet depositing or delivery have to be closed by thecovering means.

In accordance with a further feature of the invention, the air-volumechamber has a bottom wall formed with a basal surface, the outletopenings being formed in the bottom wall.

In accordance with an added feature of the invention, the bottom wall isa perforated plate. In accordance with an alternate feature of theinvention, the bottom wall is a plate formed with a multiplicity ofround holes therein. The round-hole plate may correspond, for example,to German Industrial Norm (DIN) 24 041. The round-hole plate may becovered by an appropriate surface material; partial regions of themaximum sheet format corresponding to the basal surface may, forexample, be sealed by covering plates or foils. The covering plates orfoils may be laid on supporting grids or the like which are disposed ata given spaced distance from the bottom wall of the air-volume chamberso that the covering means may be received thereat. It is alsoconceivable to use adhesive foils which are stuck onto the basal surfacewherein the outlet openings are formed, thereby sealing the respectiveoutlet openings.

In accordance with an additional feature of the invention, the bottomwall is formed, at least in part, of ferromagnetic material.

In accordance with yet all other feature of the invention, the coveringmeans are a magnetic covering.

In accordance with alternate features of the invention, the magneticcovering is formed of at least one magnetic plate and/or at least onemagnetic foil.

The form and size of the magnetic plate or foil meet the respectiverequirements, and the magnetic plate or foil is provided so as tomagnetically adhere tightly to the ferromagnetic bottom wall in anappropriate position for the purpose of sealing certain outlet openings.In particular, plastic or synthetic magnetic foils may be used forsealing purposes; with the aid of a pair of scissors, the pressman maycut the foils as required and can suitably place them so that theyadhere to the bottom wall of the air-volume chamber for controlling airdiffusion or distribution.

In accordance with yet an added feature of the invention, the coveringmeans are formed of a plurality of individual covers.

In accordance with yet an added feature of the invention, the air-volumechamber is formed with a plurality of sectional or sub-chambers. Thispermits air to be zonally blown onto the sheet, so that the sectionalchambers may be individually subjected to air. For relatively smallsheet formats, it is possible, for example, not to supply the marginalsectional chambers with air so that the area onto which air is blowncorresponds to the sheet-format area. It is also conceivable to subjectthe sectional chambers to varying air-flow intensities in order to blowair more-or-less intensely onto selective areas of the sheets to bedelivered.

In accordance with yet an additional feature of the invention,partitions are disposed in the air-volume chamber and define thesectional chambers.

In accordance with another feature of the invention, separate air-intakeconnections, respectively, communicate with each of the sectionalchambers.

In accordance with a concomitant feature of the invention, an air-intakecontrol device is connected to the air-intake connections for supplyingan individually determinable air flow therethrough to each of thesectional chambers. Each of the air-intake connections is individuallycontrollable.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin an air-flow generating device for a sheet delivery of a sheet-fedprinting machine, it is nevertheless not intended to be limited to thedetails shown, since various modifications and structural changes may bemade therein without departing from the spirit of the invention andwithin the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a sheet delivery of a sheet-fed printingmachine incorporating therein an air-flow generating device according tothe invention;

FIG. 2 is a diagrammatic perspective and partly schematic view of theair-flow generating device and a device for receiving a sheet pile; and

FIG. 3 is an enlarged fragmentary view of the air-flow generating deviceof FIG. 2 taken in the direction of the arrow III.

Referring now to the drawings and, first, particularly to FIG. 1thereof, there is shown therein a sheet delivery 1 of a sheet-fedprinting machine having a non-illustrated sheet-conveying devicepreferably constructed as a delivery gripper system for conveyingprinted sheets coming from a non-illustrated printing unit at highspeed. Grippers of the delivery gripper system open to release theprinted sheets, the velocity of the printed sheets being braked by asuction roller or sheet braking device 2, and the sheets being depositedon a device 3 for receiving a sheet pile to be formed in this manner.The device 3 is formed with a stop 4 for respective leading edges of thesheets, stops 5 (FIG. 2) for respective lateral edges of the sheets, anda deposit or delivery table 6 which is lowered in accordance with theheight of the sheet pile being formed. Above the device 3 is an air-flowgenerating device 7 which serves to effect a targeted or selective sheetdeposit or delivery onto the sheet pile. A vertical air flow or currentemerges from the air-flow generating device 7 and, inter alia, increasesthe velocity of descent of the respective sheet, thus exerts aninfluence upon the sheet depositing or delivery behavior.

In particular, FIG. 2 shows a constructional realization or embodimentof the air-flow generating device 7 as an air volume chamber 8 havingthe shape of a cuboidal or parallelepipedal hollow body with a bottomwall 10 having a basal surface 9, a ceiling or top wall 11, side walls12, a front end wall 13 and a rear end wall 14. The area of the basalsurface 9 of the air-volume chamber 8 corresponds approximately to themaximally possible sheet format which can be produced on the sheet-fedprinting machine.

Three partitions 15 extending parallel to the side walls 12 are disposedwithin the air-volume chamber 8 and divide the inner volume of theair-volume chamber 8 into four, preferably equal, sectional orsub-chambers 16. Four air-intake connections or unions 17 are providedin the rear end wall 14, each thereof leading into a respectivesectional chamber 16 and being connected to an air-intake control device19 via a pipe or hose connection 18. A main air-intake line 20 suppliesthe air-intake control device 19. The main air-in-take line 20 isconnected to a non-illustrated compressed-air source or a compressor.

As is apparent from FIG. 3, which is a fragmentary view of FIG. 2 in thedirection of the arrow III towards the air volume chamber 8, the bottomwall 10 is penetrated by outlet openings 21 which are uniformlydistributed over the entire basal surface 9 of the air-volume chamber 8.The bottom wall 10 is preferably formed of a ferromagnetic round-holeplate, particularly of the type which meets the requirements of GermanIndustrial Norms (DIN) 24 041. Magnetic foils 22 of varying planar formare arranged on the bottom wall 10 so as to adhere magnetically thereto,the magnetic foils 22, in accordance with the shape and positionthereof, covering or sealing the respective outlet openings 21 which areinvolved. In this respect, the magnetic foils 22 form a covering 23 bymeans of which air-flow intensity and air diffusion of the air flow orcurrent escaping from the perforated bottom wall 10 of the air-volumechamber 8 can be adjusted as desired.

The sheet delivery according to the invention operates in the followingmanner: The velocity at which the printed sheets are conveyed,approximately horizontally, to the vicinity of the device 3 forreceiving the sheet pile is slowed down or braked by the suction roller2, and the sheets abut the sheet leading-edge stop 4. Moreover, thesheets are guided through the space between the lateral paper stops 5.They are seized simultaneously by the air flow formed by the air-flowgenerating device 7 and accelerated thereby, as well as deliveredprecisely aligned and in a guided manner onto the delivery or deposittable 6 already having a sheet pile formed thereon. By means of thecovering 23 formed of one or more suitably arranged and shaped magneticfoils 22 magnetically adhering to the bottom wall 10 of the air-volumechamber 8, a selected number of the outlet openings 21 are covered orsealed so that not even any partial air flows are able to escapetherethrough. The result thereof is that the sheets to be deposited ordelivered are subjected to an air-flow intensity and air diffusion whichhas been adjusted by the covering 23, these air parameters having thusbeen adjusted very gradually and selectively over the entire basalsurface 9 due to the large number of outlets 21 and the many possibleways of covering them. By appropriately arranging the magnetic foils 22,the printing format, the motif or subject formation, the ink/dampeningmedium distribution and, if necessary, the resulting waviness of thesheet to be delivered, for example, may be taken into account.

By means of the strips 24 of the magnetic foils 22 disposed close to theedge of the bottom wall 10, for example, as shown in FIG. 3, it is thusconceivable to construct conventional air blast or blowing-air tubes orpipes by leaving only the marginal outlets 21 free as rows of holes.Moreover, it is also conceivable to achieve a quite special airdiffusion by constructing the magnetic foils 22, as shown in FIG. 3, inthe form of squares and rectangles 26, respectively, having cut-outs orapertures 27 provided therein, or in the form of circles 25, so that thesheets subjected to the air flow may be individually blown on by theblowing air therefrom.

If a change in a printing job should occur, the pressman may possiblyhave to alter the covering 23 by, for example, taking into account achanged sheet format and/or a different motif or subject and/or adifferent type of printing material or paper with respect to the agreedor complete printing job. For standard printing jobs, the pressman mayprepare in advance or make-ready coverings 23 which he can readilyexchange for a previously used covering 23. The magnetic foils 22 mayalso be provided without problem on the bottom wall 10 of the air-volumechamber 8 so that regions thereof overlap.

The sheet delivery constructed in accordance with the invention may, ina very simple and rapid, finely controllable manner, be adapted to thevarying delivery or depositing behavior of different printing products.It is not difficult to achieve a swift and reliable, reproducible sheetdeposit or delivery, even at extremely high printing speeds.

Because the air-volume chamber 8, as shown in FIG. 2, is divided intoseveral sectional or sub-chambers 16, a zonal control of the air-intakefeed is possible. This is effected by the air-intake control device 19which, in accordance with another embodiment of the invention, may alsobe constructed as a control valve. By means of the air-intake controldevice 19, the main air flow supplied by a suitable non-illustratedproduction device via the main air-intake line 20 is split individuallyand fed to the individual sectional or sub-chambers 16 via the pipe andhose connections 18, respectively, and via the air-intake connections orunions 17. Thus, it is possible, for example, to supply a sectional orsub-chamber 16 with more or less air flow. Moreover, it is possible toblock a respective pipe and hose connection 18 completely so that no airflow may escape from the respective sectional or sub-chamber 16.

It is possible, of course, to provide a greater number of sectional orsub-chambers 16, in comparison with those of the embodiment of theinvention shown in FIG. 2, or to partition the sectional or sub-chambers16 differently by, for example, providing further partitions extendingparallel to the end walls 13 and 14, respectively, in addition to thepartitions 15. A grid formed of partitions is thereby attainable, eachpartition field being provided with an air-intake connection or union 17so that it is possible to activate respective outlet openings 21 in avery fine screening or scanning grid.

The foregoing is a description corresponding in substance to GermanApplication P 42 13 020.4, dated Apr. 21, 1992, the Internationalpriority of which is being claimed for the instant application, andwhich is hereby made part of this application. Any materialdiscrepancies between the foregoing specification and the aforementionedcorresponding German application are to be resolved in favor of thelatter.

I claim:
 1. A sheet delivery apparatus for a sheet-processing machinehaving a sheet-conveying device for successively conveying sheets to adevice for receiving a sheet pile thereon, comprising a device disposedabove a sheet-pile receiving device for generating an air flow tofacilitate with air depositing of the sheets upon the pile-receivingdevice, said air-flow generating device having an air-suppliedair-volume chamber having a basal surface and formed with outletopenings distributed over said basal surface thereof, said basal surfacehaving an area corresponding approximately to a maximum sheet format;and covering means for sealing at least some of said outlet openings soas to adjust at least one of air-flow intensity and air diffusion of airescaping from said air-volume chamber.
 2. The sheet delivery apparatusaccording to claim 1, wherein said air-volume chamber has a bottom walldefining said basal surface, said outlet openings being formed in saidbottom wall.
 3. The sheet delivery apparatus according to claim 2,wherein said bottom wall is a perforated plate.
 4. The sheet deliveryapparatus according to claim 2, wherein said bottom wall is a plateformed with a multiplicity of round holes therein.
 5. The sheet deliveryapparatus according to claim 2, wherein said bottom wall is formed, atleast in part, of ferromagnetic material.
 6. The sheet deliveryapparatus according to claim 1, wherein said covering means are amagnetic covering.
 7. The sheet delivery apparatus according to claim 6,wherein said magnetic covering comprises at least one of a magneticplate and a magnetic foil.
 8. The sheet delivery apparatus according toclaim 1, wherein said covering means are formed of a plurality ofindividual covers.
 9. The sheet delivery apparatus according to claim 1,wherein said air-volume chamber is formed with a plurality of sectionalchambers.
 10. The sheet delivery apparatus according to claim 9,including partitions disposed in said air-volume chamber and definingsaid sectional chambers.
 11. The sheet delivery apparatus according toclaim 9, including separate air-intake connections, respectively,communicating with each of said sectional chambers.
 12. The sheetdelivery apparatus according to claim 11, including an air-intakecontrol device connected to said air-intake connections for supplying anindividually determinable air flow therethrough to each of saidsectional chambers.